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  • Access DB Transaction on insert or updating

    - by Raju Gujarati
    I am going to implement the database access layer of the Window application using C#. The database (.accdb) is located to the project files. When it comes to two notebooks (clients) connecting to one access database through switches, it throws DBConcurrency Exception Error. My target is to check the timestamp of the sql executed first and then run the sql . Would you please provide me some guidelines to achieve this ? The below is my code protected void btnTransaction_Click(object sender, EventArgs e) { string custID = txtID.Text; string CompName = txtCompany.Text; string contact = txtContact.Text; string city = txtCity.Text; string connString = ConfigurationManager.ConnectionStrings["CustomersDatabase"].ConnectionString; OleDbConnection connection = new OleDbConnection(connString); connection.Open(); OleDbCommand command = new OleDbCommand(); command.Connection = connection; OleDbTransaction transaction = connection.BeginTransaction(); command.Transaction = transaction; try { command.CommandText = "INSERT INTO Customers(CustomerID, CompanyName, ContactName, City, Country) VALUES(@CustomerID, @CompanyName, @ContactName, @City, @Country)"; command.CommandType = CommandType.Text; command.Parameters.AddWithValue("@CustomerID", custID); command.Parameters.AddWithValue("@CompanyName", CompName); command.Parameters.AddWithValue("@ContactName", contact); command.Parameters.AddWithValue("@City", city); command.ExecuteNonQuery(); command.CommandText = "UPDATE Customers SET ContactName = @ContactName2 WHERE CustomerID = @CustomerID2"; command.CommandType = CommandType.Text; command.Parameters.AddWithValue("@CustomerID2", custIDUpdate); command.Parameters.AddWithValue("@ContactName2", contactUpdate); command.ExecuteNonQuery(); adapter.Fill(table); GridView1.DataSource = table; GridView1.DataBind(); transaction.Commit(); lblMessage.Text = "Transaction successfully completed"; } catch (Exception ex) { transaction.Rollback(); lblMessage.Text = "Transaction is not completed"; } finally { connection.Close(); } }

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  • While in a transaction, how can reads to an affected row be prevented until the transaction is done?

    - by Mahn
    I'm fairly sure this has a simple solution, but I haven't been able to find it so far. Provided an InnoDB MySQL database with the isolation level set to SERIALIZABLE, and given the following operation: BEGIN WORK; SELECT * FROM users WHERE userID=1; UPDATE users SET credits=100 WHERE userID=1; COMMIT; I would like to make sure that as soon as the select inside the transaction is issued, the row corresponding to userID=1 is locked for reads until the transaction is done. As it stands now, UPDATEs to this row will wait for the transaction to be finished if it is in process, but SELECTs simply will read the previous value. I understand this is the expected behaviour in this case, but I wonder if there is a way to lock the row in such a way that SELECTs will also wait until the transaction is finished to return the values? The reason I'm looking for that is that at some point, and with enough concurrent users, it could happen that while the previous transaction is in process someone else reads the "credits" to calculate something else. Ideally the code run by that someone else should wait for the transaction to finish to use the new value, because otherwise it could lead to irreversible desync issues. Note that I don't want to lock the entire table for reads, just the specific row. Also, I could add a boolean "locked" field to the tables and set it to 1 every time I'm starting a transaction but I don't really feel this is the most elegant solution here, unless there is absolutely no other way to handle this through mysql directly.

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  • SQL SERVER – Concurrency Basics – Guest Post by Vinod Kumar

    - by pinaldave
    This guest post is by Vinod Kumar. Vinod Kumar has worked with SQL Server extensively since joining the industry over a decade ago. Working on various versions from SQL Server 7.0, Oracle 7.3 and other database technologies – he now works with the Microsoft Technology Center (MTC) as a Technology Architect. Let us read the blog post in Vinod’s own voice. Learning is always fun when it comes to SQL Server and learning the basics again can be more fun. I did write about Transaction Logs and recovery over my blogs and the concept of simplifying the basics is a challenge. In the real world we always see checks and queues for a process – say railway reservation, banks, customer supports etc there is a process of line and queue to facilitate everyone. Shorter the queue higher is the efficiency of system (a.k.a higher is the concurrency). Every database does implement this using checks like locking, blocking mechanisms and they implement the standards in a way to facilitate higher concurrency. In this post, let us talk about the topic of Concurrency and what are the various aspects that one needs to know about concurrency inside SQL Server. Let us learn the concepts as one-liners: Concurrency can be defined as the ability of multiple processes to access or change shared data at the same time. The greater the number of concurrent user processes that can be active without interfering with each other, the greater the concurrency of the database system. Concurrency is reduced when a process that is changing data prevents other processes from reading that data or when a process that is reading data prevents other processes from changing that data. Concurrency is also affected when multiple processes are attempting to change the same data simultaneously. Two approaches to managing concurrent data access: Optimistic Concurrency Model Pessimistic Concurrency Model Concurrency Models Pessimistic Concurrency Default behavior: acquire locks to block access to data that another process is using. Assumes that enough data modification operations are in the system that any given read operation is likely affected by a data modification made by another user (assumes conflicts will occur). Avoids conflicts by acquiring a lock on data being read so no other processes can modify that data. Also acquires locks on data being modified so no other processes can access the data for either reading or modifying. Readers block writer, writers block readers and writers. Optimistic Concurrency Assumes that there are sufficiently few conflicting data modification operations in the system that any single transaction is unlikely to modify data that another transaction is modifying. Default behavior of optimistic concurrency is to use row versioning to allow data readers to see the state of the data before the modification occurs. Older versions of the data are saved so a process reading data can see the data as it was when the process started reading and not affected by any changes being made to that data. Processes modifying the data is unaffected by processes reading the data because the reader is accessing a saved version of the data rows. Readers do not block writers and writers do not block readers, but, writers can and will block writers. Transaction Processing A transaction is the basic unit of work in SQL Server. Transaction consists of SQL commands that read and update the database but the update is not considered final until a COMMIT command is issued (at least for an explicit transaction: marked with a BEGIN TRAN and the end is marked by a COMMIT TRAN or ROLLBACK TRAN). Transactions must exhibit all the ACID properties of a transaction. ACID Properties Transaction processing must guarantee the consistency and recoverability of SQL Server databases. Ensures all transactions are performed as a single unit of work regardless of hardware or system failure. A – Atomicity C – Consistency I – Isolation D- Durability Atomicity: Each transaction is treated as all or nothing – it either commits or aborts. Consistency: ensures that a transaction won’t allow the system to arrive at an incorrect logical state – the data must always be logically correct.  Consistency is honored even in the event of a system failure. Isolation: separates concurrent transactions from the updates of other incomplete transactions. SQL Server accomplishes isolation among transactions by locking data or creating row versions. Durability: After a transaction commits, the durability property ensures that the effects of the transaction persist even if a system failure occurs. If a system failure occurs while a transaction is in progress, the transaction is completely undone, leaving no partial effects on data. Transaction Dependencies In addition to supporting all four ACID properties, a transaction might exhibit few other behaviors (known as dependency problems or consistency problems). Lost Updates: Occur when two processes read the same data and both manipulate the data, changing its value and then both try to update the original data to the new value. The second process might overwrite the first update completely. Dirty Reads: Occurs when a process reads uncommitted data. If one process has changed data but not yet committed the change, another process reading the data will read it in an inconsistent state. Non-repeatable Reads: A read is non-repeatable if a process might get different values when reading the same data in two reads within the same transaction. This can happen when another process changes the data in between the reads that the first process is doing. Phantoms: Occurs when membership in a set changes. It occurs if two SELECT operations using the same predicate in the same transaction return a different number of rows. Isolation Levels SQL Server supports 5 isolation levels that control the behavior of read operations. Read Uncommitted All behaviors except for lost updates are possible. Implemented by allowing the read operations to not take any locks, and because of this, it won’t be blocked by conflicting locks acquired by other processes. The process can read data that another process has modified but not yet committed. When using the read uncommitted isolation level and scanning an entire table, SQL Server can decide to do an allocation order scan (in page-number order) instead of a logical order scan (following page pointers). If another process doing concurrent operations changes data and move rows to a new location in the table, the allocation order scan can end up reading the same row twice. Also can happen if you have read a row before it is updated and then an update moves the row to a higher page number than your scan encounters later. Performing an allocation order scan under Read Uncommitted can cause you to miss a row completely – can happen when a row on a high page number that hasn’t been read yet is updated and moved to a lower page number that has already been read. Read Committed Two varieties of read committed isolation: optimistic and pessimistic (default). Ensures that a read never reads data that another application hasn’t committed. If another transaction is updating data and has exclusive locks on data, your transaction will have to wait for the locks to be released. Your transaction must put share locks on data that are visited, which means that data might be unavailable for others to use. A share lock doesn’t prevent others from reading but prevents them from updating. Read committed (snapshot) ensures that an operation never reads uncommitted data, but not by forcing other processes to wait. SQL Server generates a version of the changed row with its previous committed values. Data being changed is still locked but other processes can see the previous versions of the data as it was before the update operation began. Repeatable Read This is a Pessimistic isolation level. Ensures that if a transaction revisits data or a query is reissued the data doesn’t change. That is, issuing the same query twice within a transaction cannot pickup any changes to data values made by another user’s transaction because no changes can be made by other transactions. However, this does allow phantom rows to appear. Preventing non-repeatable read is a desirable safeguard but cost is that all shared locks in a transaction must be held until the completion of the transaction. Snapshot Snapshot Isolation (SI) is an optimistic isolation level. Allows for processes to read older versions of committed data if the current version is locked. Difference between snapshot and read committed has to do with how old the older versions have to be. It’s possible to have two transactions executing simultaneously that give us a result that is not possible in any serial execution. Serializable This is the strongest of the pessimistic isolation level. Adds to repeatable read isolation level by ensuring that if a query is reissued rows were not added in the interim, i.e, phantoms do not appear. Preventing phantoms is another desirable safeguard, but cost of this extra safeguard is similar to that of repeatable read – all shared locks in a transaction must be held until the transaction completes. In addition serializable isolation level requires that you lock data that has been read but also data that doesn’t exist. Ex: if a SELECT returned no rows, you want it to return no. rows when the query is reissued. This is implemented in SQL Server by a special kind of lock called the key-range lock. Key-range locks require that there be an index on the column that defines the range of values. If there is no index on the column, serializable isolation requires a table lock. Gets its name from the fact that running multiple serializable transactions at the same time is equivalent of running them one at a time. Now that we understand the basics of what concurrency is, the subsequent blog posts will try to bring out the basics around locking, blocking, deadlocks because they are the fundamental blocks that make concurrency possible. Now if you are with me – let us continue learning for SQL Server Locking Basics. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Concurrency

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  • INSERT and transaction serialization in PostreSQL

    - by Alexander
    I have a question. Transaction isolation level is set to serializable. When the one user opens a transaction and INSERTs or UPDATEs data in "table1" and then another user opens a transaction and tries to INSERT data to the same table, does the second user need to wait 'til the first user commits the transaction?

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  • MySQL: automatic rollback on transaction failure

    - by praksant
    Is there any way to set MySQL to rollback any transaction on first error/warning automatically? Now if everything goes well, it commits, but on failure it leaves transaction open and on another start of transaction it commits incomplete changes from failed transaction. (I'm executing queries from php, but i don't want to check in php for failure, as it would make more calls between mysql server and webserver.) Thank you

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  • INSERT and transaction searilization in PostreSQL

    - by Alexander
    Hello! I have a question. Transaction isolation level set to serializable. When the one user open transaction and INSERT or UPDATE data in "table1" and then another user open transaction and try to INSERT data to the same table is second user need to wait 'til the first user commits the transaction?

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  • MSDTC - Communication with the underlying transaction manager has failed (Firewall open, MSDTC network access on)

    - by SocialAddict
    I'm having problems with my ASP.NET web forms system. It worked on our test server but now we are putting it live one of the servers is within a DMZ and the SQL server is outside of that (on our network still though - although a different subnet) I have open up the firewall completely between these two boxes to see if that was the issue and it still gives the error message "Communication with the underlying transaction manager has failed" whenever we try and use the "TransactionScope". We can access the data for retrieval it's just transactions that break it. We have also used msdtc ping to test the connection and with the amendments on the firewall that pings successfully, but the same error occurs! How do i resolve this error? Any help would be great as we have a system to go live today. Panic :) Edit: I have created a more straightforward test page with a transaction as below and this works fine. Could a nested transaction cause this kind of error and if so why would this only cause an issue when using a live box in a dmz with a firewall? AuditRepository auditRepository = new AuditRepository(); try { using (TransactionScope scope = new TransactionScope()) { auditRepository.Add(DateTime.Now, 1, "TEST-TRANSACTIONS#1", 1); auditRepository.Save(); auditRepository.Add(DateTime.Now, 1, "TEST-TRANSACTIONS#2", 1); auditRepository.Save(); scope.Complete(); } } catch (Exception ex) { Response.Write("Test Error For Transaction: " + ex.Message + "<br />" + ex.StackTrace); }

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  • how to troubleshoot sql server issues

    - by joe
    i have an ASP .net application with sql server database, and i am wondering if you can give your ideas on how to troubleshoot the following issue: i can insert / update / delete from any table, but i have one page that uses transactions to insert into different tables. the c# code is correct and very simple, but it fails. i used the sql profiler to see how my app interacts with the DB, especially that the app is using stored procedures, i can catch the exec procedure statement and run it manually from SSMS and it works fine, but the same stored procedure fails from the application!!! which lead me to think that issue is coming from the user account and settings, i am no expert in sql server and wondering if anyone can explain how to verify the required settings for user account. thanks EDIT: in web.config here is how i reference my connection <connectionStrings> <add name="Conn" connectionString="Data Source=localhost;Initial Catalog=myDB;Persist Security Info=True;User ID=DbUser;Password=password1254_3" providerName="System.Data.SqlClient"> </connectionstring> EDIT: i will try to describe the process here: 1- i begin a transaction 2- i call a stored proc to insert (which succeeds) and return the scope identity ( that will be used in the next step) 3- i call another stored procedure to insert some more info + scope identity from step 2, which is a foreign key here 4- i get error, foreign key violation 5- transaction rolled back, now tables empty again... thanks

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  • NHibernate Session per Call in WCF - How to Rollback

    - by Corey Coogan
    I've implemented some components to use WCF with both an IoC Container (StructureMap) and the Session per Call pattern. The NHibernate stuff is most taken from here: http://realfiction.net/Content/Entry/133. It seems to be OK, but I want to open a transaction with each call and commit at the end, rather than just Flush() which how its being done in the article. Here's where I am running into some problems and could use some advice. I haven't figured out a good way to rollback. I realize I can check the CommunicationState and if there's an exception, rollback, like so: public void Detach(InstanceContext owner) { if (Session != null) { try { if(owner.State == CommunicationState.Faulted) RollbackTransaction(); else CommitTransaction(); } finally { Session.Dispose(); } } } void CommitTransaction() { if(Session.Transaction != null && Session.Transaction.IsActive) Session.Transaction.Commit(); } void RollbackTransaction() { if (Session.Transaction != null && Session.Transaction.IsActive) Session.Transaction.Rollback(); } However, I almost never return a faulted state from a service call. I would typically handle the exception and return an appropriate indicator on my response object and rollback the transaction myself. The only way I can think of handling this would be to inject not only repositories into my WCF services, but also an ISession so I can rollback and handle the way I want. That doesn't sit well with me and seems kind of leaky. Anyone else handling the same problem?

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  • How can I have 2 ADO access methods use the same Transaction?

    - by KevinDeus
    I'm writing a test to see if my LINQ to Entity statement works.. I'll be using this for others if I can get this concept going.. my intention here is to INSERT a record with ADO, then verify it can be queried with LINQ, and then ROLLBACK the whole thing at the end. I'm using ADO to insert because I don't want to use the object or the entity model that I am testing. I figure that a plain ADO INSERT should do fine. problem is.. they both use different types of connections. is it possible to have these 2 different data access methods use the same TRANSACTION so I can roll it back?? _conn = new SqlConnection(_connectionString); _conn.Open(); _trans = _conn.BeginTransaction(); var x = new SqlCommand("INSERT INTO Table1(ID, LastName, FirstName, DateOfBirth) values('127', 'test2', 'user', '2-12-1939');", _conn); x.ExecuteNonQuery(); //So far, so good. Adding a record to the table. //at this point, we need to do **_trans.Commit()** here because our Entity code can't use the same connection. Then I have to manually delete in the TestHarness.TearDown.. I'd like to eliminate this step //(this code is in another object, I'll include it for brevity. Imagine that I passed the connection in) //check to see if it is there using (var ctx = new XEntities(_conn)) //can't do this.. _conn is not an EntityConnection! { var retVal = (from m in ctx.Table1 where m.first_name == "test2" where m.last_name == "user" where m.Date_of_Birth == "2-12-1939" where m.ID == 127 select m).FirstOrDefault(); return (retVal != null); } //Do test.. Assert.BlahBlah(); _trans.Rollback();

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  • Backing Up Transaction Logs to Tape?

    - by David Stein
    I'm about to put my database in Full Recovery Model and start taking transaction log backups. I am taking a full nightly backup to another server and later in the evening this file and many others are backed up to tape. My question is this. I will take hourly (or more if necessary) t-log backups and store them on the other server as well. However, if my full backups are passing DBCC and integrity checks, do I need to put my T-Logs on tape? If someone wants point in time recovery to yesterday at 2pm, I would need the previous full backup and the transaction logs. However, other than that case, if I know my full back ups are good, is there value in keeping the previous day's transaction log backups?

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  • Under what circumstances is an SqlConnection automatically enlisted in an ambient TransactionScope T

    - by Triynko
    What does it mean for an SqlConnection to be "enlisted" in a transaction? Does it simply mean that commands I execute on the connection will participate in the transaction? If so, under what circumstances is an SqlConnection automatically enlisted in an ambient TransactionScope Transaction? See questions in code comments. My guess to each question's answer follows each question in parenthesis. Scenario 1: Opening connections INSIDE a transaction scope using (TransactionScope scope = new TransactionScope()) using (SqlConnection conn = ConnectToDB()) { // Q1: Is connection automatically enlisted in transaction? (Yes?) // // Q2: If I open (and run commands on) a second connection now, // with an identical connection string, // what, if any, is the relationship of this second connection to the first? // // Q3: Will this second connection's automatic enlistment // in the current transaction scope cause the transaction to be // escalated to a distributed transaction? (Yes?) } Scenario 2: Using connections INSIDE a transaction scope that were opened OUTSIDE of it //Assume no ambient transaction active now SqlConnection new_or_existing_connection = ConnectToDB(); //or passed in as method parameter using (TransactionScope scope = new TransactionScope()) { // Connection was opened before transaction scope was created // Q4: If I start executing commands on the connection now, // will it automatically become enlisted in the current transaction scope? (No?) // // Q5: If not enlisted, will commands I execute on the connection now // participate in the ambient transaction? (No?) // // Q6: If commands on this connection are // not participating in the current transaction, will they be committed // even if rollback the current transaction scope? (Yes?) // // If my thoughts are correct, all of the above is disturbing, // because it would look like I'm executing commands // in a transaction scope, when in fact I'm not at all, // until I do the following... // // Now enlisting existing connection in current transaction conn.EnlistTransaction( Transaction.Current ); // // Q7: Does the above method explicitly enlist the pre-existing connection // in the current ambient transaction, so that commands I // execute on the connection now participate in the // ambient transaction? (Yes?) // // Q8: If the existing connection was already enlisted in a transaction // when I called the above method, what would happen? Might an error be thrown? (Probably?) // // Q9: If the existing connection was already enlisted in a transaction // and I did NOT call the above method to enlist it, would any commands // I execute on it participate in it's existing transaction rather than // the current transaction scope. (Yes?) }

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  • Can I ask Postgresql to ignore errors within a transaction

    - by fmark
    I use Postgresql with the PostGIS extensions for ad-hoc spatial analysis. I generally construct and issue SQL queries by hand from within psql. I always wrap an analysis session within a transaction, so if I issue a destructive query I can roll it back. However, when I issue a query that contains an error, it cancels the transaction. Any further queries elicit the following warning: ERROR: current transaction is aborted, commands ignored until end of transaction block Is there a way I can turn this behaviour off? It is tiresome to rollback the transaction and rerun previous queries every time I make a typo.

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  • Transaction & Locks Problem

    - by jay
    with in do transaction, i defined a label and in this label i am accessing a table with exclusive-lock.and at the end of label i have done all the changes in that table. bt now i am with in transaction block. Now, i tried to access that same table in another session.then it show an error, Table used by another user. So is it possible that, can we release teh table with in transaction,so another user can access it. Exe Session1) DO TRANSACTION: loopb: repeat: -- --------------------- control is here right now. end. /repeat/ -- end /do transaction/ Session2) I tried to access same table,bt it show an error,that table locked by another user.

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  • Transaction & Locks Problem

    - by jay
    with in do transaction, i defined a label and in this label i am accessing a table with exclusive-lock.and at the end of label i have done all the changes in that table. bt now i am with in transaction block. Now, i tried to access that same table in another session.then it show an error, Table used by another user. So is it possible that, can we release teh table with in transaction,so another user can access it. Exe Session1) DO TRANSACTION: loopb: repeat: -- --------------------- control is here right now. end. /repeat/ -- end /do transaction/ Session2) I tried to access same table,bt it show an error,that table locked by another user.

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  • Direct web URL to PayPal transaction

    - by tags2k
    Having implemented PayPal's Website Payments Standard, I'd like to link to the details view of a transaction from my site's back end - just a simple direct web URL to the PayPal side. I don't know why this is tricky but when I try to get it from being logged in to the PayPal system it seems very obfuscated, in this form: history.paypal.com/uk/cgi-bin/webscr?cmd=_history-details&info=[looks like some kind of GUID]&ptype=4&history_cache=[huge encoded string] I'm guessing it's by design but it's not very helpful if you want a quick way to jump to a transaction's details. I've tried the https://www.paypal.com/vst/id=1234 form (also with co.uk as I am UK-based) recommended on a few sites I saw in my search, but I am told that: The transaction ID in your link is invalid. This happens even when copying the transaction ID directly from PayPal's back-end order listing. Is there a reliable way to directly link to an order / transaction details page in PayPal?

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  • With NHibernate and Transaction do I rollback on commit failure or does it auto rollback on single c

    - by mattcodes
    I've built the following Dispose method for my Unit Of Work which essentially wraps the active NH session & transaction (transaction set as variable after opening session as to not be replaced if NH session gets new transaction after error) public void Dispose() { Func<ITransaction,bool> transactionStateOkayFunc = trans => trans != null && trans.IsActive && !trans.WasRolledBack; try { if(transactionStateOkayFunc(this.transaction)) { if (HasErrored) { transaction.Rollback(); } else { try { transaction.Commit(); } catch (Exception) { if(transactionStateOkayFunc(transaction)) transaction.Rollback(); throw; } } } } finally { if(transaction != null) transaction.Dispose(); if(session.IsOpen) session.Close(); } I can't help feeling that code is a little bloated, will a transaction automatically rollback is a discrete Commit fails in the case of non-nested transactions? Will Commit or Rollback automatically Dipose the transaction? If not will Session.Close() automatically dispose the associated transaction?

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  • Geek City: What gets logged for index rebuild operations?

    - by Kalen Delaney
    This blog post was inspired by a question from a future student. Someone who was already booked for my SQL Server Internals class in June asked for some information on a current problem he was having with transaction log writes causing excessive wait times during index rebuild operations when run in ONLINE mode. He wanted to know if switching to BULK_LOGGED recovery could help. I knew the difference between ALTER INDEX in FULL vs BULK_LOGGED recovery when doing normal OFFLINE rebuilds, but I wasn't...(read more)

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  • JDBC transaction dead-lock solution required?

    - by user49767
    It's a scenario described my friend and challenged to find solution. He is using Oracle database and JDBC connection with read committed as transaction isolation level. In one of the transaction, he updates a record and executes selects statement and commits the transaction. when everything happening within single thread, things are fine. But when multiple requests are handled, dead-lock happens. Thread-A updates a record. Thread B updates another record. Thread-A issues select statement and waits for Thread-B's transaction to complete the commit operation. Thread-B issues select statement and waits for Thread-A's transaction to complete the commit operation. Now above causes dead-lock. Since they use command pattern, the base framework allows to issue commit only once (at the end of all the db operation), so they are unable to issue commit immediately after select statement. My argument was Thread-A supposed to select all the records which are committed and hence should not be issue. But he said that Thread-A will surely wait till Thread-B commits the record. is that true? What are all the ways, to avoid the above issue? is it possible to change isolation-level? (without changing underlying java framework) Little information about base framework, it is something similar to Struts action, their each and every request handled by one action, transaction begins before execution and commits after execution.

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  • Common Properties: Consolidating Loan, Purchase, Inventory and Sale tables into one Transaction tabl

    - by Frank Computer
    Pawnshop Application: I have separate tables for Loan, Purchase, Inventory & Sales transactions. Each tables rows are joined to their respective customer rows by: customer.pk [serial] = loan.fk [integer]; = purchase.fk [integer]; = inventory.fk [integer]; = sale.fk [integer]; Since there are so many common properties within the four tables, I consolidated the four tables into one table called "transaction", where a column: transaction.trx_type char(1) {L=Loan, P=Purchase, I=Inventory, S=Sale} Scenario: A customer initially pawns merchandise, makes a couple of interest payments, then decides he wants to sell the merchandise to the pawnshop, who then places merchandise in Inventory and eventually sells it to another customer. I designed a generic transaction table where for example: transaction.main_amount DECIMAL(7,2) in a loan transaction holds the pawn amount, in a purchase holds the purchase price, in inventory and sale holds sale price. This is clearly a denormalized design, but has made programming alot easier and improved performance. Any type of transaction can now be performed from within one screen, without the need to change to different tables.

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  • SQL SERVER – Monitoring SQL Server Database Transaction Log Space Growth – DBCC SQLPERF(logspace) – Puzzle for You

    - by pinaldave
    First of all – if you are going to say this is very old subject, I agree this is very (very) old subject. I believe in earlier time we used to have this only option to monitor Log Space. As new version of SQL Server released we all equipped with DMV, Performance Counters, Extended Events and much more new enhancements. However, during all this year, I have always used DBCC SQLPERF(logspace) to get the details of the logs. It may be because when I started my career I remember this command and it did what I wanted all the time. Recently I have received interesting question and I thought, I should request your help. However, before I request your help, let us see traditional usage of DBCC SQLPERF(logspace). Every time I have to get the details of the log I ran following script. Additionally, I liked to store the details of the when the log file snapshot was taken as well so I can go back and know the status log file growth. This gives me a fair estimation when the log file was growing. CREATE TABLE dbo.logSpaceUsage ( id INT IDENTITY (1,1), logDate DATETIME DEFAULT GETDATE(), databaseName SYSNAME, logSize DECIMAL(18,5), logSpaceUsed DECIMAL(18,5), [status] INT ) GO INSERT INTO dbo.logSpaceUsage (databaseName, logSize, logSpaceUsed, [status]) EXEC ('DBCC SQLPERF(logspace)') GO SELECT * FROM dbo.logSpaceUsage GO I used to record the details of log file growth every hour of the day and then we used to plot charts using reporting services (and excel in much earlier times). Well, if you look at the script above it is very simple script. Now here is the puzzle for you. Puzzle 1: Write a script based on a table which gives you the time period when there was highest growth based on the data stored in the table. Puzzle 2: Write a script based on a table which gives you the amount of the log file growth from the beginning of the table to the latest recording of the data. You may have to run above script at some interval to get the various data samples of the log file to answer above puzzles. To make things simple, I am giving you sample script with expected answers listed below for both of the puzzle. Here is the sample query for puzzle: -- This is sample query for puzzle CREATE TABLE dbo.logSpaceUsage ( id INT IDENTITY (1,1), logDate DATETIME DEFAULT GETDATE(), databaseName SYSNAME, logSize DECIMAL(18,5), logSpaceUsed DECIMAL(18,5), [status] INT ) GO INSERT INTO dbo.logSpaceUsage (databaseName, logDate, logSize, logSpaceUsed, [status]) SELECT 'SampleDB1', '2012-07-01 7:00:00.000', 5, 10, 0 UNION ALL SELECT 'SampleDB1', '2012-07-01 9:00:00.000', 16, 10, 0 UNION ALL SELECT 'SampleDB1', '2012-07-01 11:00:00.000', 9, 10, 0 UNION ALL SELECT 'SampleDB1', '2012-07-01 14:00:00.000', 18, 10, 0 UNION ALL SELECT 'SampleDB3', '2012-06-01 7:00:00.000', 5, 10, 0 UNION ALL SELECT 'SampleDB3', '2012-06-04 7:00:00.000', 15, 10, 0 UNION ALL SELECT 'SampleDB3', '2012-06-09 7:00:00.000', 25, 10, 0 GO Expected Result of Puzzle 1 You will notice that there are two entries for database SampleDB3 as there were two instances of the log file grows with the same value. Expected Result of Puzzle 2 Well, please a comment with valid answer and I will post valid answers with due credit next week. Not to mention that winners will get a surprise gift from me. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: DBCC

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  • IPC linux huge transaction

    - by poly
    I'm building and application that requires huge transactions/sec of data and I need to use IPC to for the mutithreaded mutliprocceses communication, I know that there are a lot of methods to be used but not sure which one to choose for this application. This is what the application is gonna have, 4 processes, each process has 4 threads, the data chunk that needs to be transferred between two or more threads is around 400KB. I found that fifo is good choice except that it's 64K which is not that big so i'll need to modify and recompile the kernel but not sure if this is the right thing to do? Anyway, I'm open to any suggestions and I'd like to squeeze your experience in this :) and I appreciate it in advance.

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  • Update transaction in SQL Server 2008 R2 from ASP.Net not working

    - by Amarus
    Hello! Even though I've been a stalker here for ages, this is the first post I'm making. Hopefully, it won't end here and more optimistically future posts might actually be me trying to give a hand to someone else, I do owe this community that much and more. Now, what I'm trying to do is simple and most probably the reason behind it not working is my own stupidity. However, I'm stumped here. I'm working on an ASP.Net website that interacts with an SQL Server 2008 R2 database. So far everything has been going okay but updating a row (or more) just won't work. I even tried copying and pasting code from this site and others but it's always the same thing. In short: No exception or errors are shown when the update command executes (it even gives the correct count of affected rows) but no changes are actually made on the database. Here's a simplified version of my code (the original had more commands and tons of parameters each, but even when it's like this it doesn't work): protected void btSubmit_Click(object sender, EventArgs e) { using (SqlConnection connection = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["ApplicationServices"].ConnectionString)) { string commandString = "UPDATE [impoundLotAlpha].[dbo].[Vehicle]" + "SET [VehicleMake] = @VehicleMake" + " WHERE [ComplaintID] = @ComplaintID"; using (SqlCommand command = new SqlCommand(commandString, connection)) { SqlTransaction transaction = null; try { command.Connection.Open(); transaction = connection.BeginTransaction(IsolationLevel.Serializable); command.Transaction = transaction; SqlParameter complaintID = new SqlParameter("@complaintID", SqlDbType.Int); complaintID.Value = HttpContext.Current.Request.QueryString["complaintID"]; command.Parameters.Add(complaintID); SqlParameter VehicleMake = new SqlParameter("@VehicleMake", SqlDbType.VarChar, 20); VehicleMake.Value = tbVehicleMake.Text; command.Parameters.Add(VehicleMake); command.ExecuteNonQuery(); transaction.Commit(); } catch { transaction.Rollback(); throw; } finally { connection.Close(); } } } } I've tried this with the "SqlTransaction" stuff and without it and nothing changes. Also, since I'm doing multiple updates at once, I want to have them act as a single transaction. I've found that it can be either done like this or by use of the classes included in the System.Transactions namespace (CommittableTransaction, TransactionScope...). I tried all I could find but didn't get any different results. The connection string in web.config is as follows: <connectionStrings> <add name="ApplicationServices" connectionString="Data Source=localhost;Initial Catalog=ImpoundLotAlpha;Integrated Security=True" providerName="System.Data.SqlClient"/> </connectionStrings> So, tldr; version: What is the mistake that I did with that record update attempt? (Figured it out, check below if you're having a similar issue.) What is the best method to gather multiple update commands as a single transaction? Thanks in advance for any kind of help and/or suggestions! Edit: It seems that I was lacking some sleep yesterday cause this time it only took me 5 minutes to figure out my mistake. Apparently the update was working properly but I failed to notice that the textbox values were being overwritten in Page_Load. For some reason I had this part commented: if (IsPostBack) return; The second part of the question still stands. But should I post this as an answer to my own question or keep it like this?

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